Grate mechanism for automatic stokers



Feb. 27, 1945.

F. O. WALLENE GRATE MECHANISM FOR AUTOMATIC STOKERS Filed Feb. 4, 1943 3 Sheets-Sheet 1 INVENTOR FRAN/f 0. WALLENE BY WAM/@v ATTO R N EYS Feb. 27, 1945.

F. o. WALLEN 2,370,274

GRATE MECHANISM FORAUTOMATIC STOKERS 3 Sheets-Sheet 2 Filed Feb. 4, 1943 L7/- 6 INVENTOR FIM/VK 0. MJLLENE l BY H ATTORNEY v Feb. 27, |1945. v F. o. wALLENE 2,370,274

GRATE MECHANISM FOR AUTOMATIC STOKERS Filed Feb. 4, 1945 3 Sheets-Sheet 3 ggf/0 INV-ENTOR FPA/vk 0. WALL/ENE ATTO R N EYS Patented Feb. 27, 1945 VGRA'IE MECHANISM FOR AUTOMATIC STOKERS Frank 0. Wallene, Cleveland, Ohio, assignor to The Johnston & Jennings Company, Cleveland, Ohio, a corporation of Chio Application February 4, 1943, Serial No. 474,686

4 Claims.

This invention relates to automatic stoker mechanism, and more Aparticularly to the manner and means of controlling the air spacesor openings through the grate for the purpose of securing and maintaining uniform air distribution over the entire grate area and to the fuel bed supported upon the grate.

More particularly, the invention relates to that type of automatic stoker in Which the fuel bed is supported by chain sections which travel side by side either along a slope. or generally horizontally. The chain sections form a floor or table which supports the bed of fuel, which is usually hopper fed to the chains at one end thereof and is carried by them slowly along the length of the fire box to the farend thereof, where ashes are discharged. In some cases, adjoining chain sections, ordinarily side by side, are separated by intervening so-called stationary tuyres or grate bars which have no travelling movement. In these types of Stoker, air is supplied to the'fuel bed by way of ports or openings through the stationary bars or chain links, or through clearance spaces between chain links or sections or between chain sections and stationary bars.

One object of the invention is to provide structural improvement in stoker mechanism of the character described which avoids uneven burnling caused by uneven distribution of air supply at different areas of the grate surface and therefore to the fuel bed.

A further object of the invention is to provide an improved construction of this kind in which, instead of compelling the movable chain sections to travel longitudinally over fixed and unvarying paths, they are ,permitted lateral self-accommodating or floating motion, i. e., motion at right angles to their path of travel, and further are subjected to confinement in contact with each other or with adjacent stationary grates by yielding pressure applied from the sides, an arrangement which maintains the clearance spaces at the preselectedsize throughout the range of travel of the chain section and which consequently insures and maintains uniform air distribution throughout the length and breadth of the fuel grate area.

A further object of the invention is to provide, in a chain grate embodying the relatively stationary intervening longitudinal bars before referred to, an improved arrangement in which said bars, (possibly excepting the row along the longitudinal center line), while still immovable longitudinally of the fuel bed, are permitted lateral movement like unto that of the chain sections, for similarly maintaining contact along the sides of the outer chain links and the stationary bars, but permitting both chain sections and bars to go and come,

'while still maintaining uniform port area and distribution of air over the entire fuel bed.

A further improvement is to provide, in a construction of the character described, sealing means along the side edges of the grate preventing ley-passing of air around the grate members and avoiding inflow or leakage of air along the side zones of the fuel bed.

A further object is to provide a simple and improved form cf yieldable mechanism for maintaining proper relation of the chain sections with each other, and with the stationary bars if such are present, for the purposes described, and further enabling the pressure mechanism to be readily set or adjusted initially and to be further adjusted, during the life, of the Stoker mechanism, if occasion requires.

Still another object of the invention is to provide an improved form of driving and guiding mechanism for the several grate chains, with especial reference to the supporting and operating parts between the grate chains and the driving shaft at one end and the idler shaft at the other end of the furnace, so as to provide full floating free` self-accommodation of the chains to any` conditions that may arise over a period of furnace use. I Further objects of the invention are in part obvious and in part will appear more in detail hereinafter.

In the drawings, which represent one suitable lembodiment of the invention, Fig. 1 is a longitudinal sectional elevation, partly diagrammatic, on approximately the line I I, Fig. 2; Fig. 2 is a detail cross section, on a larger scale, on the line 2 2, Fig. 1; Fig. 3 is a detail sectional plan view, onapproximately the line 3 3, Fig. 1; Fig. 4 is a detail sectional elevation on the line 4 4, Fig. 2; Fig. 5 is a plan view of a portion of the grate shown in Fig. 1; Fig. 6 is a detail sectional elevation on the line 6 6, Fig. 1; Fig. 7 is a detail section, corresponding to Fig. 1, but on a Alarger scale, showing one of the driving sprockets; Fig. 8 is a section on the line 8 8, Fig. '7;l

Fig. 9 is a, view corresponding to Fig. 7, showing a modification; and Fig. 10 is a sectional view on the line ID I0, Fig. 9.

The furnace as a whole may be of any suitable or desired form and requires but brief description.

It includes the combustion chamber I formed by the furnace walls 2 and a oor, marked genfloor ofthe furnace chamber and upon whichthe fuel -bed is supported may be made up entirely of a series of end-less chain sections, such as those indicated at I0, lying side by side, the several chain sections travelling over sprockets I I on the front or drive shaft I2 and at the lower end over a suitable support on the rear idler shaft I3. In

the arrangement shown in the drawings, liwe ever, the chain sections are spaced apart laterally, and between each two adjacent chain sections lies a longitudinally extending relatively stationary Bar li heid against longitudinal movementfso that it does not partake of the travel of or have longitudinal motion like the links of the chain sections. A given furnace or, when made entirely of 'chain sections, may consist of any 'suitable oi' desired number thereof (as many as forty or more)and may be of any desired length, and when iliade of invable chain sectifo'lis'A lying parallel and separated by intervening relatively stationary bars, may likewise consist of any desired number fchain sections and bars and be ofany suitable length. y

The chain 'sections may be 'of any suitable or desired forni, usually each thereof `being made up of a Vseries of links, such as inner links I0a and outer links IUb, fastened together by pivot pins II)'c.:` Some ai'r 'for lcombustion may be permitted to fi'ow through the clearance spaces Ibfvetvvee'n links, such 'as by way f 'cavities l 5 and slts I5d. Ifheir particular arrangement or configuration fQi this pl'rp'os'e is; not impbftant. The stationary bars I4 may also f any suitable form in cross section, either made of -separate parts secured together, as by bolts', or, as shown, lthe stationary bars may be generally of box-like form in cross section, as in Fig. 2`, their Aouter or side faces being of such configuration as to 'provide clearance spaces IB forming open ports 6r 'pssages between the stationary bars and movable chain sections, for the passage 'of air f' Acomb'usti'o'n between them.

In constructions or this kind, involving movable chain sections, as 'stated hereinabove, the upper runs of the `chain sections, on which the fuel bed is supported, usually are compelled to travel each through an invariable path, vby the provision "o'f longitudinally extending guides for the chain sections. Further, the stationary bars I4 usually are firmly secured in place so 'as to have no mo'- tion laterally of thefurnace chamber. In 4the present construction, both the in'ovable chain sec'- tions and the relatively stationary bars have lateral movement. y

The upper runs ofthe chains, 'and also the stationary bars, vrat their bottoms rest upon skid or supporting plates I1, which in turn 'rest up'o'n the upper flanges of channel Vmembers vI8 extending crosswise of the furnace chamber land distributeclvat intervals along the same, as shovinin Fig. 1. Thus, tneskid pistes i1 merely form venting direct contact thereof with the flanges of channels I8 and Kreducing wear. Preferably the several skid plates are provided with lugs I9, Fig. 4, extending downwardly and confining them in their positions upon the channel flanges.

For the purposes before described, means is provided, effective crosswise of the furnace chamber, for maintaining close contact between the chain sections and bars. The means provided for this purpose is as follows:

Along each side of the furnace is located the usual ledge plate 20. This ledge plate, in the present construction, extends horizontally, with its lower surface in the same plane as the upper surfaces of the movable chain sections and stationary bars.- Along the outer edge of the chain grate is a. longitudinally extending relatively stationary side bar 22, immovable longitudinally, but having lateral movement, and the upper surface of which extends beneath the inner edge of the ledge plate. Distributed at intervals along this outer bar 22 is a series of cams or arms 23, yieldingly pressed inwardly or against the side of the bar by any suitable means. In the arrangement 'shown each cam or arm is fastened to the upper end of a rod or shaft 24, to the lower end of each of which is fastened an arm 25, the free end of which is in contact with one end of a compression spring 28, the other end of which engages an abutment 21 on a bolt or rod 28 fastened at its other end to a suitable fixed support conventionally shown at 29; Such devices are distributed at intervals of every two or three feet along the grate and on either or both sides thereonas may be desirable.

In some cases the outermost bar 22 along one edge of the furnace may engage the fixed or stah tionary outer wall or abutment 40, adjustable cams 23 and their operating devices being employed only along one edge of the furnace. However, to reduce the maximum lateral travel req'uired 'of any chain section or relatively station'- ary bar, and as shown, movable bars 22 and cams 23 may be used along both side edges of the fun nace, working in opposition or toward each other. 'Such an arrangement is particularly useful in the 'wider furnace In this case, one of the skid plates Il has itsI lug I9 bolted at I9a to the cross beam IB and is also Drov'ledY with 'an upwardly' Aextending lug lsb entering a recess in the center stationary bar I4 and preventing it from moving laterally.

In installing the stoker mechanism, after all 'of the stationary bars and endless chai-n sections have been `laid in place', they are pushed together or `into Contact transversely of the furnace; the several cams 23 are then turned to bring them into engagement with the outermost plate or plates` 22, and 'ar-'ms Zi'ar'e then rotated upon shafts y2'4 until they engage with vthe ends of 4the springs 26. Arms 25 are then fixedly secured to shafts 24. When this adjustment has been completed over the enti-re furnace, it is clear that at no point along the length 4of 'the furnace chamber can the chain -sections and bars have relative lateral movement, such Aas movement of separation, without swinging one or more of the 23, rotating the vcorresponding shafts 24 and compressing springs 26. If desired, in the original set-up, the springs 26`may be placed under some initial compression, but Vusually this is unnecessary a'nd undesirable 'because it 'increases friction 'and' we'a'r. -But any 'event the chain sections and bars hug 'each other `closely during 'travel 'of the "chains over the full vlength of the furnaoe chamber, and such air ports or openings as are gamma formed by clearance spaces between them are ing is desirable to insure uniform distribution of f.

air throughout the fire bed area. But the ordinary automatic stokers, of chain grate form, do

Knot provide such uniform distribution through those ports or openings formed by interengaging l It is interfered with relatively movable parts. by a number of causes, such as wear on the parts,

`uneven expansion and contraction of metal, oxidation of the metal bars or grates by the rush of air past metal surfaces in a zone where there is no available fuel to combine with the air, and so forth. The arrangement described does away with these objections, avoids excess leakage and rthe ow of unnecessary air through the furnace relative disposition of the side plates 22 and ledge plates 20, with the side plates lying beneath the ledge platesfprovides an efficient air seal but yet ,permitting the lateral full floating movement of chain sections and bars described.

Furthermore, air ow through the lower l'half'i of the grate is usually controlled by .dampers, such as shown conventionally at 50, Fig. Leach damper controlling flow vthrough one zone of the 'from'v dropping down as they move along. Hence vthe teeth of the driving sprockets extend upwardly into said cavities for driving engagement with the-link pins Ille or other parts of the links, and very little clearance is available forrelative lateral motion between the links and sprocket teeth. l Accordingly, lateral self-accommodating floating movement of the chains, with reference to the sprocket teeth cannot be secured r-by using sprockets with teeth which are elongated (lengthwise of the shaft) and permitting the chain links lto go and come along the long teeth. The

fire bed. The cams 23 provided for the lower half of the grate are so located as to ride upon i,"

the upper flanges of the cross channelsl I8` and each cam, of course, also engages the lower surface of the plate 2l] above it. Consequently, each cam serves as a stopper or closure between the main chamber of wind box 6 and the distributing chambers 6a, and also between adjacent distributing chambers. Thus, when the dampers 50 are closed leakage or by-.passing of air around them is prevented by the cams, whatever is the position thereof.

Moreover, lateral movement of bars and chains usually makes it desirable to specially form or arrangev the mounting or supports for the chain sections. At .the discharge end of the grate, in the construction here shown, the lower ends of several of the chain sections, instead of each being supported upon its own individual sprocket upon the idler shaft I3, travel over a common long drum or roller 30, several drums being mounted in axial alinement. Each drum, for example, may support two, three or more adjacent chain sections, and several drums may be employed in a wide furnace. The drawings show three drums, which may be mounted coaxially either on` the same shaft or, as shown, upon short shaft sections arranged end to end and mounted in bearings 3|.

The chain driving mechanism, at the feed end of the grate, is also provided with means enabling the driving sprockets, or more accurately, the driving teeth thereof, to accommodate themselves to lateral movement of the chain sections through the life of the grate, and hence also to be full floating, as at the idler supports. Any suitable arrangement may be employed for the purpose.

Each chain link, it will be observed, on either side of its cavity I5, Fig. 2, has a depending side wall 4I, the lower edges of these side walls riding upon the skid plates I'I and serving to bridge the gaps between them and prevent the chain links sprockets are therefore made of special form or are so mounted upon the shafts that the links of each chain section and those sprocket teeth in engagement with chain links at any time are 'per- 'mitted to move laterally as a unit without disturbing their driving relation. This effect may be secured either by so mounting each sprocket upon the shaft as to permit the entire sprocket ring, as a unit, to move bodily along the shaft, or by mounting the sprocket teeth in the ring so as to permit the several teeth to move individually.

In Figs. 7 and 8 the rst form is illustrated. In a given furnace there may be as many as forty or more sprocket wheels keyed to vand driven by the same shaft. Each sprocket I I, for convenient assembly upon the shaft, is split into two like halves 50, 5I held together by bolts 52. The arrangement is such thaty when the clamping bolts are pulled home to bring the sprocket hub ends together, the sprocket is then not frictionally clamped upon the shaft but lis a fairly close sliding fitupon it, able to move longitudinally upon the shaft should occasion arise. Each sprocket vhalf isrkeyed to the shaft at 53, individual keys being used for each sprocket or a single long key -(or two keys) f or all the sprocketsupon a given shaft.

With this arrangement, if the chains or stationary bars grow laterally, as by oxidation, over a period of months of use, the several chain sections and their respective sprockets move laterally toward the side or sides of the furnace chamber and the driving relation is not disturbed.

In Figs. 9 and 10 the same effect is accomplished by ixedly clamping and keying each of the sprocket hubs to .the shaft and providing each sprocket with a ring having sockets 54 in which detachable teeth 55 are mounted and keyed by their configuration for movement on the ring longitudinally of the shaft.

It of course should be understood that when reference is made to lateral movement of the chains or chain links and stationary bars with reference to each other and of the sprocket teeth or sprockets lengthwise of the driving shaft,

such motion is not frequent or repeated. In other y words, the chains, bars and sprockets or sprocket y teeth do not move back and forth, f-or example, with each rotation of the driving shaft. The motion is exceedingly slow and imperceptible, taking place over a period of possibly many months of service or use of the grate. It is occasioned, for example, by very slow lateral grow-th or increase in width of the chains or stationary bars occasioned by accretions due to oxidation of the metal. But over a period of months or years, in

a grate including forty-two chains side by side,l

each six inches or so in width, the total growth or increase in width may reach the order of four or five inches. Consequently, if yielding cam bars or arms are located along one side only'of such a grate, the chains nearest to the cams. and the corresponding sprockets, might require four ,to

nve inches of. lateral free noatlng movement. and ifA resilient arms' are `used along both sides of the grate, withvthe middle chain or chains xed and lateral movement occurring 'in both directions, the maximum motion might be, up to'two and one-half inches. In either case. whether the maximum is two and one-half inches or five inches, that amount of motion is large as compared with the sprocket teeth and the link sockets into which they project, which are of the, order4 of an inch wide.

. What I claim is:

,i l. The combination in a Stoker, of a grate comprising a seriesof endless chain sections movable along generally parallel paths and also mountedfor limited self-accommodating motion laterally with respect to .each other, Yieldiner means eiective upon .the outer face of an outer .chain section and .tending to. prevent but per mitting limited outward lateral movement of the sections while moving longitudinally, and a cross shaft at one end of the grate provided with means ,supporting one end of each of the chain sections and arrangedto permit self-accommodating movement along the shaft of each chain section as it moves outwardly.`

24 The combination in a Stoker, 'of a vgrate comprising a series of endless chain sections movable along generally `parallel paths and also mounted for limited self-accommodating motion laterally with respect to each other, yielding means effective upon the outer face of an outer chain sectionv and tending .to prevent but per mittng limited outward lateral movement of the sections while moving longitudinally, a cross shaft at lone end of the grate 4for supporting one end of each of the chain-sections, and connecting -driving means between said shaft and each chain movable along generally parallel `paths section arranged to permit self-accommodating movement along `the shaft ot each chain section as it moves outwardly.

3. The combination in a Stoker, 0I a Brote comprising a series of endless chain sections mov able along generally parallel paths and also mounted for limited self-accommodating .motion laterally with respect to each other, yielding means effective upon the outer face of an outer chain section and tendini,r to prevent but permitting limited youtward lateral movement of the sections .while moving longitudinally, a cron shaft at one end of the `grate for supporting one end of each of the chain sections, said shalt carrying a series of sprocket teeth for the links of each chain section, said teeth being distributed uniformly around the shaft .axis and being mounted upon it for self-accommodating mow ment lengthwise of the shaftas the chain section moves laterally of the grate.

4. The combination in a Stoker, of a grate comprising aseries of endless chain sections and also mounted for limited sel-accommodating motion 'laterally with respect to each other, yielding means effective upon the outer face 0.1' an outer chain section'and tending to prevent but permitting limited outward lateral Amovemem'. of the sections while moving longitudinally, a driving shaftprov-ided with a series of sets of sprocket teeth, one set for each chain section, for supporting and driving one end yof each chain section, each set .of teeth being movable longitudinally of the shaft, land drum means supporting the opposite end of each chain section, whereby as any chain section tends to move laterally vit 4can so v move at each end of the grate.

FRANK O. WALLENE. 

